Circuit arrangement for use in automatic telephone system



July 3Q, 1957 w. SIX ET AL 2,301,369

CIRCUIT ARRANGEMENT FOR uss IN AUTOMATIC TELEPHONE SYSTEM Filed May 13, 1955 INVENTORS WILLEM 7 Six JACOBUS 'DOMBURG AGENT United States atent CIRCUIT ARRANGEMENT FOR USE IN AUTO- MATIC TELEPHONE SYSTEM Willem Six and Jacobus Domburg, Eindhoven, Netherlands, assignors, by mesne assignments, to North American Philips Company, Inc., New York, N. Y., a corporation of Delaware Application May 13, 1953, Serial No. 354,733

Claims priority, application Netherlands lune 1t 1952 2 Claims. (Cl. 315-845) The invention relates to circuit arrangements for use in automatic telephone systems.

It has been suggested to use in an electronic telephone system a circuit arrangement, in which dialling pulses are received by an electronic counting circuit comprising a plurality of gas-filled tubes. In these counting circuits the cathode of each of the gas-filled tubes is directly connected to the ignition electrode of a subsequent tube of the counting circuit so that the subsequent tube has a higher potential set up across its ignition electrode than the remaining tubes, when the preceding tube is conductive. The pulses are set up between the starting electrode and the cathode of the tubes. On reception of pulses of definite polarity having an amplitude exceeding a definite threshold value the counting circuit tubes strike in succession. This counting circuit acts as a marking circuit and for this purpose the cathodes of the tubes are connected to starting electrodes of additional gas-filled tubes, which act as intelligence contacts and through which in their conductive condition intelligence current may consequently flow in two directions. On reception of a given dialling pulse train a given gas-filled tube of the counting circuit remains conductive for a certain period of time, so that a numerically corresponding intelligence contact tube strikes, if the output apparatus connected thereto, for example a subscribers line, is flee. However, if this apparatus is engaged, the intelligence contact tube does not strike. It is desirable for the counting circuit to be restored to the rest position when the intelligence contact tube becomes conductive, that is to say when a connection is established. For this purpose provision ismade of an auxiliary gas-filled tube, which strikes on reception of impulses of the said definite polarity having an amplitude which exceeds a definite second threshold value which exceeds the said first threshold value, said auxiliary tube being coupled to the counting circuit tubes so as to cause them to extinguish upon ignition of the auxiliary tube. Hence the counting circuit responds both to pulses the amplitude of which exceeds the first threshold value and to pulses the amplitude 01 which exceeds the second threshold value, whereas the auxiliary tube for the extinction of the selector becomes conductive only if the pulses exceed the second threshold value. Connected in series with the main discharge path of the auxiliary gas-filled tube is an impedance such that the tube is re-extinguished automatically upon ignition. In this case there is a limitation in that, if two strong pulses are received in quick succession, for example in the case of the call being terminated by the vibration of the oft-normal contact of a subscribers telephone receiver, the first tube of the counting circuit is ignited by the first pulse, but re-extinguishes immediately upon ignition of the auxiliary tube and is re-ignited by the second pulse but in this case does not re-extinguish, since due to the action of the series impedance the auxiliary tube cannot become conductive twice in quick succession. Hence ultimately the counting circuit is not restored to the normal position.

The invention obviates this difliculty. In an arrangement according to the invention provision is made of a second auxiliary gas-filled tube, which similar to the first auxiliary gas-filled tube strikes on reception of pulses of the determined definite polarity having an amplitude exceeding the definite second threshold value and an anode of which is connected to a point of constant potential through the parallel combination of a resistor and a capacitor and in addition is directly coupled to an ignition electrode of the first counting circuit tube. In the normal position of the counting circuit the ignition electrode of the first tube has the highest potential of all the ignition electrodes, with the result that the first tube strikes at the first dialling pulse. Thus, if, for example at the end of a call, two strong pulses were received in quick sequence, the first counting circuit tube strikes at the first pulse and extinguishes immediately thereafter, but cannot restart at the second pulse, since on the second auxiliary tube becoming conductive the anode and hence the ignition elec trode of the first counting circuit tube have assumed a comparatively low potential, which due to the above-mentioned capacitor is maintained at a low value for some length of time.

The invention will now be described With reference to the accompanying diagrammatic drawing in which an embodiment thereof is shown by way of example.

Referring now to the single figure of the drawing in which part of an electronic automatic telephone exchange is shown diagrammatically the establishment of a connection between two subscribers, for example AA and AB is enabled by gas-filled tubes, for example BA and BB, which act as electronic switching contacts and the control of which is effected wholly by electronic means. The subscribers stations, for example AA, are connected through a line loop S1, S2 to ends of two identical windings of a transformer TA associated with the subscribers line LCA of the subscriber concerned. The other ends of the said windings are interconnected through a capacitor C19. and with the interposition of a resistor R12. also connected to the terminals of a supply battery BT. One end of a third winding of the transformer TA is connected to earth through a resistor R25. which is shunted by a capacitor C29. whereas the other end of the winding is connected via a multiple-wired point QA to the cathodes k of a number of gas-filled tubes BA, only one of which is shown on the drawing, the anodes a of these tubes being connected to a multiple-wired point P of a number of line circuits VC. Through an inductance L and the parallel combination of a resistor R1 and a capacitor C1 the multiple-wired point P is connected to a supply source V1, the voltage of which is for example volts. This voltage is lower than the starting voltage between anode a and cathode k of each of the gas-filled tubes, which for example is equal to volts, but exceeds the operating voltage which is 60 volts. A first ignition electrode f, is connected to a tapping on a potentiometer Rea, Rat, which is included between earth and the junction P2 of the resistor R1 and the inductance L. Through a delay network comprising resistors Rfia, R69. and capacitors C3a and Co a second ignition electrode is coupled to an output point Mz of an electronic counting circuit TS associated with the line circuit VC. The remaining subscribers lines, such as for example the line LCB of subscriber AB, is arranged similarly to that of the line-circuit LCA.

The line circuit VC comprises a vacuum tube Bo and a number of gas-filled tubes B1, B2, B3, B4 and B5, whereas the counting circuit TS comprises ten additional gas-filled tubes, of which the tubes B6, B7, and Ba only are shown in the figure. The gas-filled tubes each comprise an anode a, a cathode k and an ignition electrode f, as shown with the gas-filled tube B4.

Potential changes across the multiple-wired point P1 are amplified by the tube Bo and transmitted. with opposite polarity to a point U and thence passed on through capacitors C10, C20, C30 and C40 to the gas-filled tubes B1, B2, B3 and B4. The cathode circuits of the gas-filled tubes B1, B2 and B4 comprise a resistor which is shunted by a capacitor, with the result that when ignition has taken place these tubes extinguish automatically. For the same purpose the tube B3 comprises in its anode circuit a resistor shunted by a capacitor. The tube B1 acts to transmit dialling pulses to the counting circuit TS. The starting electrode 1 of this tube is connected through a resistor R10 to a source V2 of sufficient voltage for the tube B1 to strike on comparatively weak positive-going pulses being set up at the point .U. The tube B2 acts to restore the counting circuit to the normal position, that is to say to extinguish its tubes. Through a resistor R20 the starting electrode of tube Bzis connected to a source V3 of sufiicient voltage for the tube B3 to strike on the occurrence of comparatively strong positive-going pulses at the point U but not on the occurrence of the weaker pulses to which the tube B1 responds. The function of the tubes B4 and B5 is to restore the entire circuit to the normal position, that is to say to extinguish all the gasfilled tubes of the line circuit VC and the intelligence tubes BA and BB. The function of the tube Ba will be described later.

The counting circuit is of a type known per se. The anodes of the tubes B6 B7, Be and so forth are supplied from the voltage source V1. The cathodes are connected through resistors R60, R70, R80, and so forth to a point W, which is coupled to the cathode of the tube B2 through a capacitor C22 and connected to earth through a resistor R2. Through resistors R71, R81 etc. the cathodes of the tubes B6, B7, B8, etc. are each connected to the starting electrode of the subsequence counting circuit tube and in addition through capacitors C71, C81 etc. respectively to the cathode of the subsequent tube. In the normal position of the circuit the starting electrodes of the tubes B7, Ba, etc. are at earth potential. In contradistinction thereto the starting electrode of the tube Be is connected to a tapping on a potentiometer R31, R32, R33, which is included between the supply point V1 and earth and to an additional tapping on which the anode of the tube B is connected. If the tube B3 is not conductive, the starting electrode of the tube Be is at a potential which is slightly lower than the striking voltage between this electrode and the cathode, so that normally the starting electrode of the tube Be is at the highest of the potentials of the starting electrodes of the counting circuit tubes. The starting electrodes of the tubes B6, B7, B8, etc. are coupled to the cathode of tube B1 through capacitors C60, C'm, C80, etc.

Whenever tube B1 strikes due to the occurrence of a positive pulse at the point U the said capacitors transmit a positive pulse to the starting electrodes of the tubes B6, B7, B8, etc. As has been stated hereinbefore, in the normal position of the circuit, the starting electrode of the tube Be is at the highest potential of all the starting electrodes. Thus, at the first pulse the tube B6 will strike, with the result that the potential of the cathode of the tube Be will be increased to approximately 100 volts and the potential of the common point W to approximately 50 volts. Thus a 50 volts voltage is eifective between the starting electrode and the cathode of the tube B7 whereas the potential of the starting electrodes of the subsequent tubes Ba etc. remains equal to that of the cathode. At the second pulse the tube B7, the starting electrode of which is at a higher potential than the starting electrode of the subsequent tubes, strikes. The potential of the cathode of the tube B7 is thus increased to volts, with the result that the potential of the starting electrode of the tube B8 is also increased to 100 volts and is thus at the highest of the starting electrode potentials. The capacitor C71 transmits a positive pulse to the cathode of the tube B6 with the result that this tube extinguishes. Similarly the tube Ba will strike at the third pulse, whereupon the tube B7 extinguishes. The tube Ba does not re-ignite at the third pulse, since due to the potential increase of the point W only a comparatively low voltage is set up between its starting electrode and its cathode.

The entire circuit arrangement operates as follows:

Assuming that the subscribers AA and AB correspond to the numerals 2 and 3 respectively and the subscriber AA wants to establish a connection with the subscriber AB. On the subscriber AA lifting the receiver the line loop is closed through the intelligence conductors S1 and S2 and the subscribers station, with the result that the transformer TA transmits a negative voltage pulse to the multiple-wired point QA. The starting electrodes of the gas-filled tubes, the cathodes k of which are connected to the point QA, the anodes being connected to free line circuits, are at a potential which is slightly lower than the starting voltage between the starting electrode 1, and the cathode k with the result that due to the occurrence of the impulse at the cathodes all these tubes are brought into a condition in which they are liable to strike. As soon as one of these tubes, for example the tube BA, tends to strike, the main discharge path between the cathode k and the anode a also strikes, with the result that current tends to flow from the supply point V1 through the resistor R1, the inductance L, the intelligence conductor S, the discharge path between the anode a and the cathode k of the gas-filled tube BA concerned, the multiple-wired point QA, the winding of the transformer TA and a resistor Rza to earth. This results in a voltage drop across the resistors R1 and R29., so that the potential of the multiple-wired point P1 is reduced by 50 volts and the potential of the multiple-wired point QA is increased by 50 volts. The potential increase of the point QA prevents any other gas-filled tube coupled to this point from striking. Gas-filled tubes which couple the point QA to engaged line circuits cannot strike, since the multiple-wired points P2 of these line circuits are at a potential which is lower than volts, with the result that also the potential of the starting electrodes 1, of the gas-filled tubes concerned is considerably lower than the starting voltage. Due to the ignition of the tube BA a connection is established through this tube between the subscribers line and the line circuit VC. The negative pulse produced at the point P1 is transmitted by the tube Bo with opposite polarity to the point U and thence through the capacitors C10, C20 and C30 to the starting electrodes of the gas-filled tubes B1, B2 and Ba. Since the ignition of the tube BA results in a strong pulse at the point B1, all three of the said gas-filled tubes B1, B2 and B3 strike. Due to the ignition of the tube B1 the counting circuit tube B6 strikes in the manner described hereinbefore, but thereupon extinguishes immediately, since on the tube B2 striking a strong positive pulse is transmitted by a capacitor C22 to a point W and thence through a resistor R60 to the cathode of the tube B6. The ignition of the tube B3, which thereupon extinguishes immediately due to the presence of a capacitor C31 in the anode circuit has no further effect. A rectifier g prevents the positive pulse set up at the point U from being transmitted to the tubes B4 and B5.

The subscriber AA then dials the required number, in this case the digit 3. The subscribers dial is shunted by an impedance not shown, with the result that at each dialling impulse the line loop is not entirely broken and the pulses which during dialling are set up across the windings of the transformer TA are weaker than the pulses produced by the line loop being wholly closed or opened. At the multiple-Wired point P1 '21 positive impulse is produced at the beginning of each dialling pulse and a negative pulse at the end thereof due to the differentiating etfect of the transformer TA. The amplitude of these pulses is comparatively weak and is about 5 volts. By the tube Bu these pulses are transmitted with opposite polarity to a point U. The negative pulses have no further effect, the positive pulses, however, cause the gas-filled tube B1 to strike at intervals, with the result'that the counting circuit passes into the next counting position in the manner described hereinbefore. The pulses produced during dialling are weak enough for the gas-filled tubes B2 and B3 not to respond thereto. At 'the first dialling pulse the gas-filled tube Ba strikes, with the result that its cathode voltage is increased to 100 volts. Through a conductor M1 and a time-delay network (not shown) this cathode is coupled to the starting electrode 3, of a gas-filled tube included in the subscribers line corresponding to the digit 1. The time-delay effect of the above mentioned network prevents the voltage of the starting electrode 1, from being increased to the striking voltage, since the voltage of the cathode of the tube Be is reduced at the second dialling pulse. At the second and third pulses the tubes B7 and Bs respectively strike. Through a time-delay network comprising capacitors C3b and C41, and resistors R510 and Rsb the cathode of the tube Ba is coupled to the starting electrode f, of a gas-filled tube BB appertaining to the required subscribers line. Due to the third dialling pulse not being followed by a fourth, the voltage of the starting electrode 1, is enabled to be increased to a value at which the gas-filled tube BB strikes, if the line LCB is free. However, if subscriber AB is engaged, one of the gas-filled tubes coupled to the point QB is conductive so that resistor R2b passes current with the result that the voltage of the point QB exceeds earth potential, the gas-filled tube BB being thus prevented from striking.

Supposing the subscriber AB to be free, the gas-filled tube BB strikes and as a result ringing current is supplied to the subscribers station AB in a non-specified manner. The ignition of the gas-filled tube BB results in addition in that a strong negative pulse is produced at the point P1 and a strong positive pulse at the point U. The counting circuit will thus pass to the fourth counting position; but be extinguished immediately thereafter due to the tube B2 striking. If the subscriber AB lifts the receiver in response to the call, the closing of the line loop produces another strong negative pulse at the point P1 and consequently a strong positive pulse at the point U, with the result that the gas-filled tubes B1, B2 and B2 re-ignite, so that in the above described manner the counting circuit re-passes from its normal position to the first counting position, but is extinguished immediately thereafter when the gas-filled tube B2 strikes. Thus an intelligence connection is established between the two subscribers and intelligence currents are enabled to be transmitted in both directions through the transformer TA, the main discharge paths between the anodes and cathodes of the gas-filled tubes BA and BB and a trans former TB.

At the cessation of the call one of the subscribers replaces the receiver with the result that the associated lineloop is opened and a strong positive pulse is produced at the point P1, which as a strong negative pulse is transmitted by the tube B0 to the point U and thence through the capacitor C40 and the rectifier g to the cathode of the tube B4. The starting electrode of the tube B4 has a bias voltage preventing this tube from striking on the occurrence of comparatively weak negative pulses at the cathode, such as are produced, for example, during dialling, but enabling it to strike at a strong negative pulse. Consequently, tube B4 strikes, with the result that the cathode voltage is greatly increased and the capacitor C50 transmits a strong positive pulse to the starting electrode of the tube B5, whereupon this tube strikes. Capacitor C51 transmits a strong negative pulse to the intelligence conductor S, with the result that the anode voltages of the gas-filled tubes BA and BB are sufiiciently reduced to cause these tubes to extinguish. Tube Bo transmits this pulse with opposite polarity to the point U, the ignition of the tube B4 also resulting in a strong positive pulse being transmitted to the point U through the rectifier g and the capacitor C40. These positive pulses cause the tubes B1, B2 and B3 to strike, with the result that the counting circuit passes to the first counting position and is extinguished in the manner described hereinbefore.

. However, the difiiculty may arise that, when the receiver is replaced, the elf-normal contact of the telephone receiver continues to vibrate for a short period with the result that the line-loop is re-closed transiently and the first closing pulse is followed by a second one. The first pulse produces the effect described hereinbefore, but on the line-loop being re-closed the gas-filled tube BA re-strikes, since it still contains a great many ions. Due to the second pulse the counting circuit will re-respond, whereopon the tube Bs strikes, the counting circuit, however, will not be extinguished since the tube B2 cannot strike twice in quick succession, due to the cathode voltage of this tube being still maintained upon ignition at a high value for some time due to the presence of a capacitor C21.

This difliculty is obviated by the provision of the gasfilled tube Ba. As stated hereinbefore, this tube strikes when a strong positive pulse is produced at the point U, since its starting electrode similar to that of the tube B2 is connected to the supply point Va. The anode thus assumes a comparatively low voltage with the result that the voltage of the starting electrode of the tube B6 is A also greatly reduced. Imparting a very high value to the capacitor C31 permits of maintaining the voltage of the starting electrode of the tube Be at a low value for a comparatively long period of time. If the closing pulse were succeeded by a supplementary pulse, the gas-filled tube B1, which is adjusted in a comparatively critical manner, would re-strike, but not the tube Be.

What is claimed is:

1. A circuit-arrangement in an automatic telephone system comprising an electronic counting circuit including a plurality of successive gas-filled electric discharge tubes connected in succession from a first tube thereof to a last tube thereof and adapted to ignite in succession on reception of pulses of definite polarity having an amplitude exceeding a first predetermined value, each of said tubes having an ignition electrode and a cathode, each of said cathodes being coupled electrically to the ignition electrode and to the cathode of the subsequent tube of said plurality of tubes, a source of signalling pulses connected to the ignition electrode of said first tube, an output circuit connected to derive counted pulses from said last tube, a first auxiliary circuit including a first auxiliary gas-filled electric discharge tube and a first self-extinguishing circuit electrically coupled thereto, said first auxiliary tube being adapted to ignite on reception of pulses of said definite polarity having an amplitude exceeding a second predetermined value which is greater than said first predetermined value, said first auxiliary tube being coupled electrically to said plurality of successive tubes so as to cause said latter-named tubes to extinguish upon ignition of said first auxiliary tube, and a second auxiliary circuit including a second auxiliary gas-filled electric discharge tube having an anode and a second selfextinguishing circuit coupled electrically thereto and including a parallel combination of a resistor and a capacitor connected between a point of constant potential and the second auxiliary tube anode and means coupling electrically said second auxiliary tube anode to the ignition electrode of said first tube of said plurality of successive tubes, said second auxiliary tube being adapted to ignite on reception of pulses of said definite polarity having an amplitude exceeding that of said second predetermined value.

2. A circuit arrangement in an automatic telephone system comprising an electronic counting circuit including a plurality of successive gas-filled electricdischarge tubes connected in succession from a first tube thereof to a last tube thereof and adapted to ignite in succession on reception of pulses of definite polarity having an amplitude exceeding a first predetermined value," eachof said tubes having an ignition electrode and a cathode, each of said cathodes being coupled electrically to the ignition electrode and to the cathode of the subsequent tube of said plurality of tubes, at source of signalling pulses connected to the ignition electrode of said first tube, an output circuit connected to derive counted pulses from said last tube, a first auxiliary circuit including a first auxiliary gas-filled electric discharge tube and a first self-extinguishing circuit coupled electrically thereto, said first auxiliary tube being adapted to ignite on reception of pulses of said definite polarity having an amplitude exceeding a second predetermined value which is greater than said first predetermined value, said first auxiliary tube being 20 coupled electrically to each cathode of said plurality of tubes so as to cause said latter-named tubes to extinguish upon ignition of said first auxiliary tube, and a second auxiliary circuit including a second auxiliary gas-filledelectric-discharge tubehaving an anode and a second selfextinguishing'circuit coupled'electrically thereto and in-' cluding a parallel combination of a first resistor'and a capacitor connected between a first point of-constant potential and said second auxiliary tube anode, a second resistor and a third resistor forming a series connection with said second resistor, said series-connected resistors being connected between said second auxiliary tube anode and a second point of constant potential, the junction of said second and third resistors being coupled electrically to the ignition electrode of said first tube of said plurality of successive tubes, said second auxiliary tube being adapted to ignite on reception of pulses of said definite polarity having an amplitude exceeding said second predetermined value.

Mumma Aug. 26, 1947 Mumma Oct. 3, 1950 

